In recent years, with progress of digital technology and improvement in data compression technology, information recording media for recording computer programs, music information, video information (contents), etc., which include optical disks, such as CD (compact disk) and DVD (digital versatile disk), have come to attract attention. And inexpensive optical disk devices for performing recording of information to such an optical disk and reproducing of information from the optical disk have come to spread.
What are currently marketed as rewritable optical disks are CD-RW (CD-rewritable), DVD-RAM, DVD-RW (DVD-rewritable), DVD+RW (DVD+rewritable), etc.
Meanwhile, the amount of information of video information or contents tends to increase year by year, and it is expected that the amount of information that is recordable on a single optical disk, i.e., the storage capacity, will further increase.
For this reason, the development of an optical disk having a plurality of rewritable recording layers is performed energetically. However, there is a problem that at the time of recording (or reproducing) of information to a target recording layer of such a multilayered optical disk, which is distant from the plane of incidence of the irradiated light beam, the target recording layer is influenced not a little by a recording state of another recording layer of the disk nearer than the target recording layer to the plane of incidence. For example, see Japanese Laid-Open Patent Application No. 2004-327038.
The influence depends on the material characteristics of the optical disk concerned, and it is not necessarily simple. Although the optical disk having the plurality of rewritable recording layers is not marketed currently, the above-mentioned problem is one of the issues which should be cleared for commercial production.